A switch of this type finds many applications, and it may for instance be used in equipment for handling high electric power for switching high voltages (which may be 2-400 kV) and currents, for example in surge diverters, currents limiters, and the like. An advantage of a switch of this type is that irradiation control provides for very fast switching, which is of particular importance in high power applications for protection of equipment when faults occur.
One problem with such switches is that some materials which might be candidates to be used as the first material will have a columnar-grain structure and will accordingly be polycrystalline, although a mono-crystalline structure is preferable. These columns will extend substantially vertically between the two sides of the first layer, and as the contact electrodes are applied on opposite sides of the first layer, the grain boundaries formed by the columns may act as potential short-circuit paths between the contact electrodes thereby substantially reducing the breakdown field of the switch and increasing the intensity of leakage currents. This problem is, for example, there for CVD diamond, which it is very difficult to grow mono-crystalline, and the risk is high that impurities, e.g. graphite, are gathered in the grain boundaries, so that the level of the voltage across the contact electrodes which the switch will be conducting in the blocking (open) state will be reduced considerably.